1. Field of the Invention
The present invention relates to a poly fuse burning system, and in particular relates to a poly fuse burning system capable of monitoring the burning state of the poly fuse.
2. Description of the Related Art
In computing, eFUSE is a technology which allows for the dynamic real-time reprogramming of computer chips. Speaking abstractly, computer logic is generally ‘etched’ or ‘hard-coded’ onto a chip and cannot be changed after the chip has finished being manufactured. By utilizing the eFUSE technology, a chip manufacturer can allow for the circuits on a chip to change while it is in operation. The eFUSE technology tunes performance or power consumption of a chip by burning out some convenient and ordinary poly fuses. If certain sub-systems fail, take too long to respond, or are consuming too much power, a chip can instantly change its behavior by burning poly fuses.
FIG. 1 is a diagram showing a conventional poly fuse burning system. As shown in FIG. 1, in the conventional poly fuse burning method, a voltage source which outputs a high voltage is mainly used to burn a poly fuse during a predetermined time interval. FIG. 1 shows a poly fuse burning system 10 comprising a poly fuse 12, a voltage source 14, a programmed pulse controller 16, and a switch M.
The voltage source 14 provides a high and fixed voltage level to burn the poly fuse 12. When the programmed pulse controller 16 turns on the switch M, a burning current flows through the poly fuse 12 for burning; when the programmed pulse controller 16 turns off the switch M, the burning current stop flowing through the poly fuse 12 to stop the burning. Namely, the programmed pulse controller 16 is used to control a pulse width for burning the poly fuse 12.
However, for the above poly fuse burning method, there is a problem with tuning of the pulse width. If the pulse width is too wide (that is, the pulse width is wider than a pulse width just capable of burning out the poly fuse), some metal materials may melt and then flow to the hole produced by the destroyed poly fuse because of overheat, causing the resistance across the poly fuse to fall suddenly, which would lead to an undesired state. If the pulse width is too narrow (that is, the pulse width is narrower than a pulse width just capable of burning out the poly fuse), a number of inspections for checking whether the poly fuse is burnt out is necessary, and the pulse may be provided many times until the poly fuse is burnt out.
In the burning method described above, the pulse width which is enough to burn out each poly fuse poly may be different for many kinds of poly fuses. Therefore, manufacturer's need to spend time on testing which pulse width is appropriate to burn out a kind of poly fuse.
Meanwhile, the voltage source can also provide a gradually rising voltage level to burn the poly fuse. FIG. 2 is a voltage-current curve diagram of when a poly fuse is being burnt. As shown in FIG. 2, when the voltage applied by the voltage source stays within a range from 0V to 3V, the poly fuse is not yet been burnt out, and the current flowing through the poly fuse is roughly proportional to the voltage applied by the voltage source. Meanwhile, when the voltage applied by the voltage source surpasses 3V, the poly fuse burns out, and the current flowing through the poly fuse falls suddenly because the resistance across the poly fuse rises substantially. In an ideal case, the poly fuse is burnt out, so the current value can remain at an extremely low value after the voltage applied by the voltage source surpasses 3V. However, as shown in FIG. 2, when the voltage source continues to raise the output voltage, the current value will rise several times. That is, an undesired state, as mentioned above, which is caused by some metal materials melting and flowing to the hole produced by the destroyed poly fuse for overheat when the voltage level applied by the voltage source is too high or the burning duration is too long.
As described above, in the conventional poly fuse burning method, whether controlling the pulse width (or burning duration) or the voltage level, control of continuing or stopping of the burning of the poly fuse according to the burning state of the poly fuse can not be instantaneously controlled. Also, it is difficult to adjust the pulse width or the voltage level for various kinds of poly fuses. Furthermore, the resistance of the poly fuse may become low through time, so the conventional poly fuse burning method which controls the duration or the voltage level to burn the poly fuse can only determine whether the poly fuse is burnt out or not. However, the burning degree of the poly fuse is unable to be precisely controlled.